Joint effect of nitrogen and phosphorus concentrations on citric acid production by different strains of Aspergillus niger grown on an effluent

Summary The joint effects of the initial concentration of N and P on the production of citric acid by 11 strains of Aspergillus niger on an effluent are studied by means of orthogonal full-factorial 2² designs. The results allow the definition of a series of empirical equations describing well differentiated types of behaviour. This demonstrates the usefulness of the procedure followed in order to establish selection criteria for the more suitable strains, to determine the tendencies that permit approaching optimum production and evaluate the viability of different culture options characterized by discontinuous feeding of one or another nutrient.     

A high-throughput microscale method to release N-linked oligosaccharides from glycoproteins for matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analysis

This report describes a convenient method for the rapid and efficient release of N-linked oligosaccharides from low microgram amounts of glycoproteins. A 96-well MultiScreen assay system containing a polyvinylidene difluoride (PVDF) membrane is employed to immobilize glycoproteins for subsequent enzymatic deglycosylation. Recombinant tissue-type plasminogen activator (rt-PA) is used to demonstrate the deglycosylation of 0.1-50 micrograms of a glycoprotein. This method enabled the recovery of a sufficient amount of N-linked oligosaccharides released enzymatically with peptide N-glycosidase F (PNGaseF) from as little as 0.5 microgram rt-PA for subsequent analysis by matrix-assisted laser desorption/ionization time-of-flight (MALDI- TOF) mass spectrometry. The immobilization of rt-PA to the PVDF membrane did not sterically inhibit the PNGaseF-mediated release of oligosaccharides from rt-PA as determined by tryptic mapping experiments. Comparison of the oligosaccharides released from 50 micrograms of rt-PA by either the 96-well plate method or by a standard solution digestion procedure showed no significant differences in the profiles obtained by high-pH anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Both neutral and sialylated oligosaccharide standards spiked into wells were recovered equally as determined by HPAEC-PAD. One advantage of this approach is that reduction and alkylation can be performed on submicrogram amounts of glycoproteins with easy removal of reagents prior to PNGaseF digestion. In addition, this method allows 60 glycoprotein samples to be deglycosylated in 1 day with MALDI-TOF or HPAEC-PAD analysis being performed on the following day.      

Irradiation induces G2/M cell cycle arrest and apoptosis in p53-deficient lymphoblastic leukemia cells without affecting Bcl-2 and Bax expression

The tumor suppressor p53 has been implicated in gamma irradiation-induced apoptosis. To investigate possible consequences of wild-type p53 loss in leukemia, we studied the effect of a single dose of gamma irradiation upon p53-deficient human T-ALL (acute lymphoblastic leukemia) CCRF - CEM cells. Exposure to 3 - 96 Gy caused p53-independent cell death in a dose and time-dependent fashion. By electron microscopic and other criteria, this cell death was classified as apoptosis. At low to intermediate levels of irradiation, apoptosis was preceded by accumulation of cells in the G2/M phase of the cell division cycle. Expression of Bcl-2 and Bax were not detectably altered after irradiation. Expression of the temperature sensitive mouse p53 V135 mutant induced apoptosis on its own but only slightly increased the sensitivity of CCRF - CEM cells to gamma irradiation. Thus, in these, and perhaps other leukemia cells, a p53- and Bcl-2/Bax-independent mechanism is operative that efficiently senses irradiation effects and translates this signal into arrest in the G2/M phase of the cell cycle and subsequent apoptosis.     

Phylogenetic relationships within the Alcidae (Charadriiformes: Aves) inferred from total molecular evidence

The Alcidae is a unique assemblage of Northern Hemisphere seabirds that forage by "flying" underwater. Despite obvious affinities among the species, their evolutionary relationships are unclear. We analyzed nucleotide sequences of 1,045 base pairs of the mitochondrial cytochrome b gene and allelic profiles for 37 allozyme loci in all 22 extant species. Trees were constructed on independent and combined data sets using maximum parsimony and distance methods that correct for superimposed changes. Alternative methods of analysis produced only minor differences in relationships that were supported strongly by bootstrapping or standard error tests. Combining sequence and allozyme data into a single analysis provided the greatest number of relationships receiving strong support. Addition of published morphological and ecological data did not improve support for any additional relationship. All analyses grouped species into six distinct lineages: (1) the dovekie (Alle alle) and auks, (2) guillemots, (3) brachyramphine murrelets, (4) synthliboramphine murrelets, (5) true auklets, and (6) the rhinoceros auklet (Cerorhinca monocerata) and puffins. The two murres (genus Uria) were sister taxa, and the black guillemot (Cepphus grylle) was basal to the other guillemots. The Asian subspecies of the marbled murrelet (Brachyramphus marmoratus perdix) was the most divergent brachyramphine murrelet, and two distinct lineages occurred within the synthliboramphine murrelets. Cassin's auklet (Ptychoramphus aleuticus) and the rhinoceros auklet were basal to the other auklets and puffins, respectively, and the Atlantic (Fratercula arctica) and horned (Fratercula corniculata) puffins were sister taxa. Several relationships among tribes, among the dovekie and auks, and among the auklets could not be resolved but resembled "star" phylogenies indicative of adaptive radiations at different depths within the trees.      

Molecular Analysis and Test of Linkage between the FMR-1 Gene and Infantile Autism in Multiplex Families

Approximately 2%–5% of autistic children show cytogenetic evidence of the fragile X syndrome. This report tests whether infantile autism in multiplex autism families arises from an unusual manifestion of the fragile X syndrome. This could arise either by expansion of the (CGG)n trinucleotide repeat in FMR-1 or from a mutation elsewhere in the gene. We studied 35 families that met stringent criteria for multiplex autism. Amplification of the trinucleotide repeat and analysis of methylation status were performed in 79 autistic children and in 31 of their unaffected siblings, by Southern blot analysis. No examples of amplified repeats were seen in the autistic or control children or in their parents or grandparents. We next examined the hypothesis that there was a mutation elsewhere in the FMR-1 gene, by linkage analysis in 32 of these families. We tested four different dominant models and a recessive model. Linkage to FMR-1 could be excluded (lod score between −24 and −62) in all models by using probes DXS548, FRAXAC1, and FRAXAC2 and the CGG repeat itself. Tests for heterogeneity in this sample were negative, and the occurrence of positive lod scores in this data set could be attributed to chance. Analysis of the data by the affected-sib method also did not show evidence for linkage of any marker to autism. These results enable us to reject the hypothesis that multiplex autism arises from expansion of the (CGG)n trinucleotide repeat in FMR-1. Further, because the overall lod scores for all probes in all models tested were highly negative, linkage to FMR-1 can also be ruled out in multiplex autistic families.